The present invention relates to a powder separating filter, particularly for alternatingly supplying different types and/or kinds of powders to a powder dispensing device such as for example a powder spray gun. The invention further relates to a powder dispensing system comprising a powder dispensing device and a powder separating filter.
Using powder dispensing devices for example in the form of manual or automatic powder spray guns to spray coat objects with coating powder is known and common in powder coating technology, whereby the powder dispensing devices usually comprise a coating powder spray head for spraying coating powder at their front end region and a coating powder connection at their opposite rear end region. Powder, coating powder in particular, can be fed to a coating powder channel extending to the coating powder spray head via the coating powder connection of the powder dispensing device.
The powder dispensing devices discussed herein relate in particular to powder dispensing devices for coating powder conveyed pneumatically in a flow of compressed air. The coating powder is sprayed through a material outlet of the coating powder spray head at the front end region of the powder dispensing device. The material outlet can be formed for example by a material channel mouth with or without a cross-deflector (impact head or the like), by a nozzle or by a rotational atomizing element.
The coating material, in particular coating powder or even liquid coating, is electrostatically charged preferably by means of static electricity and/or a high voltage of more than 1000 V, e.g. a voltage in the range of between 10,000 V and 140,000 V, in order to thereby achieve better adhesion to the—preferably grounded—object to be coated and to reduce wastage.
Such a powder dispensing device is for example described at least in principle in the DE 44 18 288 A1 printed publication. Same thereby relates to an automatic powder spraying device for the electrostatic spray coating of objects with coating material, particularly coating powder.
This known prior art powder spraying device comprises an elongated housing in the form of a gun barrel, a coating material channel extending through the housing in the housing's longitudinal direction, a nozzle for atomizing the coating material at the downstream front end of the coating material channel, and a high voltage generator accommodated in the housing. The high voltage generator thereby serves in generating a high voltage at a high voltage electrode, by means of which the coating material to be sprayed by the powder spraying device is electrostatically charged.
In this known prior art powder spraying device, all the connecting lines, in particular the connecting line for the coating material to be sprayed, the connecting line for an electrical voltage on the primary side of the high voltage generator, and the compressed air connecting line, are led through a robotic arm and connected on the rear face side of the powder spraying device at which the powder spraying device can for example be secured to a robotic arm. The compressed air supplied to the powder spraying device by way of the compressed air connecting line serves to flow around the high voltage electrode so that no coating material can accumulate on it. Compressed air can furthermore be used during a cleaning process to support the atomizing process or to blow out powder residues in the powder spraying device.
According to DE 44 18 288 A1, the respective rear face sides of a plurality of powder spraying devices are mounted on a carrier which is attached to a robotic arm at its side facing away from the powder spraying device. The high voltage generator is disposed over a powder channel extending through the housing in the housing's longitudinal direction. To accommodate the high voltage generator, the housing has a region which expands upwardly.
A powder dispensing device in the form of a powder spray gun with a powder channel for coating powder extending through its gun barrel is also known from the U.S. Pat. No. 4,196,465 printed publication, wherein the components of a high voltage generator are arranged underneath the powder channel. A handle is detachably secured to the gun barrel so that the gun barrel can also be used without the handle, for example on a stationary stand or on a lift stand or on a robotic arm. When securing the gun barrel to a stand or a robotic arm, said stand or robotic arm needs to have attached arms able to reach through an opening in a wall of a coating booth in which the gun barrel for coating objects is disposed. The connecting lines for the coating material, the electrical voltage and the compressed air likewise extend from the gun barrel through the booth's wall opening separately from each other and, when a lift stand is used, need to be looped so that their sections connected to the gun barrel can move relative to the upstream stationary line sections arranged outside the booth.
The above-described powder dispensing devices known from the prior art are in each case secured in operation to a stand or robot positioned outside of a coating booth by means of a corresponding extension, whereby the extension reaches through an opening in a wall of the coating booth.
Disadvantageous in this context is that cleaning of such powder dispensing devices, for example because of changing powder, is relatively time-consuming and laborious. This is also particularly due to not only the powder dispensing devices themselves needing to be carefully cleaned of powder residues but also the coating material lines led through the extensions, and particularly also the powder lines serving to supply the coating material to be sprayed from a powder reservoir to the coating material lines led through the extensions or the powder dispensing devices respectively.
The cleaning of the coating material lines and the powder lines routed through the extensions is frequently time-consuming since the coating material lines are often only accessible with difficulty. This usually makes it necessary to completely pull the powder dispensing devices out of the coating booth's wall opening again for cleaning purposes.
With respect to cleaning the powder lines via which the powder dispensing devices are fed the coating material to be sprayed from a powder reservoir, it is to be noted that these powder lines are usually relatively long, which likewise leads to relatively time-consuming cleaning in the case of e.g. changing colors.